What Is La Niña?


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La Niña occurs every 3-7 years in the Pacific Ocean. It is a weather pattern that generally occurs in sync with El Niño. During La Niña, winds cause warm surface water from the equator to move west which causes colder water to rise near the edge of South America. La Niña can cause more lighting and storms in South and Central America as well as in the United States. The event affects weather in different aspects all over the world. El Niño also affects weather across the globe, only in the opposite way. 

La Niña is the unusual cooling of surface waters in the tropical Pacific Ocean. El Niño is an unusual warming of surface waters in the tropical Pacific Ocean.  These events switch every 3-7 years and are in sync with each other. This weather pattern is referred to as ENSO, El Nino-Southern Oscillation (ENSO). The occurrence takes into effect several components, the largest effect being on ocean temperature. Ocean temperature also has a large effect on the wind temperature, which changes weather. Seasons are affected by these two components. During a warm year, summers get hotter and winters are warmer. During a colder year, summers are cooler and winters are colder. 

Ocean Temperature

Ocean temperatures greatly affect weather across the globe. In places where the ocean is generally warm there is more rain and clouds. These warmer places are closer to the equator and the sun heats the ocean up throughout the day. 

In years where La Niña is in effect, more rain clouds form out at sea and bring in rain from the warmer water. While this is occurring, other places in the world have drought, causing forest fires or lakes to dry up. These odd weather patterns are not uncommon during La Niña years. 

During La Niña, colder water is brought near the coast and more hurricanes form. This cold water and mixing of ocean water and nutrients generally helps fish populations and helps fisheries. La Niña generally creates more upwelling which brings nutrients to the surface for fish. 


Trade Winds generally blow to the west across the Pacific which causes cooler waters to rise to the surface and warmer water to cool in the middle of the Ocean. The movement of deeper colder water to replace warmer water is known as upwelling. 

Upwelling brings nutrients and phosphates to the surface, as well as cooler water. Phytoplankton use these to grow through photosynthesis. Many animals including clams, fish, and whales eat phytoplankton. Phytoplankton are a key for many species that provide for the South American seafood industry including anchovy, sardine, mackerel, shrimp, tuna, and hake.

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During the summer in La Niña years rainfall is stronger than usual. This usually causes the monsoon season in India and Bangladesh. This also causes flooding in Australia, and can cause massive amounts of damage. La Niña can last one to three years unlike El Niño, which generally lasts no more than a year.

The National Oceanic and Atmospheric Administration (NOAA) operates a network of scientific buoys which measure air temperatures, currents, winds, and humidity. The buoys are located in around 70 locations around the southern Pacific Ocean. This monitoring helps scientists find new details and discoveries about climate and weather effects.